Frequently Asked Questions

Here is information about joining my group!

Well, I used to try to respond to as many emails as possible, but this is no longer feasible, given the large number of inquiries I receive. Instead, I use an automated system that sends this message:

Thank you for your interest in my research!

Due to the large volume of inquiries I receive, I can't always provide individual responses.

Please visit http://jthaler.net/join for infomation about potential ways to join my research group.

If you want to get a more detailed response, then you need to make a more personal connection, at minimum by including my name in your email. Or saying that a trusted advisor (include your advisor’s name!) recommended that you contact me. Or that you are interested in a specific paper of mine (include the reference!). Even then, my inbox is overflowing with inquiries, so my system might still send the stock message.

When describing the open questions in particle physics to non-experts, it is usually necessary to paint a simplified picture using simplified language. Sometimes, though, this simplified language is used by experts when communicating to each other. Mostly this is harmless, but sometimes I find that it misleads students (and even professors!) about what the real mysteries in particle physics are.

Here are two examples where I think that the statement in bold is misleading and that the more accurate statement is more interesting than the simplified lore:

• “The Standard Model of particle physics cannot explain neutrino masses and mixings.” If by “Standard Model”, we mean a theory without right-handed neutrinos and only dimension four and smaller interactions, then this statement is true. But sometimes this statement is erroneously interpreted to imply that neutrino masses and mixing somehow expose a conceptual limitation to the Standard Model. I think it is more accurate to say: “The Standard Model of particle physics has many plausible extensions to accommodate neutrino masses and mixings, but we don’t yet know the precise mechanism at play.” Viewing the Standard Model as an Effective Field Theory, the simplest mechanism to introduce neutrino masses and mixings is the dimension-five Weinberg operator, which has the added bonus of providing a compelling scaling argument for why neutrino masses should be small but non-zero.
• “Quantum Field Theory is incompatible with General Relativity.” If by “incompatible”, we mean it can’t make predictions at arbitrarily high energies or in arbitrarily curved geometries, then this statement is true. But it is not widely appreciated that the structure of General Relativity can be derived from Quantum Field Theory. The idea is to start from the assumption that the gravitational force is mediated by a massless spin-two particle and then to work out the consistency conditions for unitary quantum behavior. Satisfyingly, this derivation explains why gravity has (and must have, by quantum consistency) a universal coupling to matter. Of course, this theory breaks down if you try to use it to describe extreme quantum gravitational phenomena, but it is a perfectly adequate theory of “quantum gravity” for phenomena experienced in our day-to-day lives.

If I am on your PhD thesis committee and you make one of the above bold statements in your thesis, then there is a high probability that I’ll ask you about it during your defense.

You mean “ABRACADABRA” (A Broadband or Resonant Approach to Cosmic Axion Detection with an Amplifying B-field Ring Apparatus)? Or “DarkLight” (Detecting A Resonance Kinematically with Leptons Incident on a Gaseous Hydrogen Target)? Or the infamous “P…B…S…” (Polynomial… Basis… for… Substructure…, see footnote 10), which would likely best the competition at DOOFAAS? I write down a sentence describing the idea, take the first letters of (most) of the words, and watch my collaborators cringe.

Token frequency analysis and large language models.

For me, taking a course in quantum mechanics from Antal Jevicki was the key turning point when I realized that I wanted to pursue theoretical physics as a career. But it was not until I went to graduate school that I realized exactly what it means to be on the front lines of scientific progress. So until you experience the simultaneous frustration and exhilaration of research, it is hard to really grasp what it means to be theoretical physicist on a day-to-day basis.

When I taught quantum mechanics myself at MIT (8.06), I gave the following advice to my students on the last day of class (mostly juniors, many of whom would go on to graduate school in physics and related fields):

• Find mentors. Even now as a faculty member, I have around five senior colleagues I regularly turn to for advice. As a younger scientist, it is even more important to have someone (and preferably multiple people) who are looking out for your best interests and giving you honest feedback. In most cases, your mentor will also be your research advisor, but it is generally a good idea to also have a mentor outside of your research group as well. Your mentors will often be your strongest advocates when it comes time to get a permanent job in academia (or elsewhere).
• Be visible. Somehow society’s image of a theoretical physicist is a lone genius toiling away in a closed office. The reality is that physics (especially theoretical physics) is a social enterprise, with many research ideas arising at the coffee machines (or at the lift lines if you go here in the winter). As a younger scientist, you might feel that the best thing you can do is focus on your specific research project and exclude the outside world, but in my experience, making yourself visible is a better way to forward your research career. This means that you should go to as many seminars and colloquia as you can (and even try to go to dinner with the speaker), as well as discuss your work regularly with people outside of your immediate research group. For me, I credit regular lunches with my Berkeley theory colleagues at this restaurant with saving me from the research doldrums (get the red rice).
• Tell a story. Science is a process of discovering the ultimate truths of nature, and while the truths themselves are independent of the research process, research itself is shaped by the personalities involved. In order to make sure that other scientists understand and appreciate your work, you need to make an effort to explain not just the results of your work, but why your work is interesting and important and how it fits into the narrative arc of the field. This means that you have to develop strong writing and presentation skills. Bland research results are difficult to appreciate, but telling a compelling story about your research (in print or in person) is a great way to engage your audience.

If you are looking for more advice, I found this transcript of a podcast by my MIT colleauge Peter Fisher to be quite enlightening (especially the part about the fish).

There are as many ways to be a successful physicist as there are successful physicists. That said, there are skills that are highly correlated with research success. So if you are motivated by checking off boxes, here are some tasks that most (though not all) graduate students in theoretical physics complete by the end of their PhD.

• Regularly attend research seminars and colloquia
• Ask a question at a research seminar/colloquium
• Read the arXiv on a semi-regular basis
• Have a favorite textbook on Quantum Field Theory (which may or may not be this)
• Become familiar with the Review of Particle Physics from the Particle Data Group
• Attend a physics summer school
• Learn to write in LaTeX
• Do the majority of calculations in a paper
• Make the majority of plots in a paper
• Write the majority of text in a paper
• Submit a paper to the arXiv (bonus points if you are top of the list)
• Submit a paper for peer review in a journal (e.g. JHEP and PRD)
• Be a peer reviewer for a journal article (often as a favor to your PhD advisor)
• Write a paper in collaboration with someone other than your PhD advisor
• Learn to prepare slides (any format is fine; I use Keynote)
• Give a blackboard presentation of any kind
• Present your research at your home institution
• Present a journal club article in a field different from your own
• Visit another institution and give a seminar
• Give a talk about your research at an international conference or workshop
• Explain your research to non-physicists
• Bonus: Develop an innovative data analysis strategy
• Optional: Make suggestions for how to improve this list

Here are three practice problems of increasing difficulty:

• Draw the leading order Feynman diagrams that contribute to top-antitop production at the Large Hadron Collider. Repeat for top-top production.
• Augment the Standard Model to have two Higgs doublets and write down all interactions with dimension four and smaller. Assuming generic couplings, why is this theory inconsistent with experimental data?
• Present a simultaneous solution to the strong CP problem, hierarchy problem, and cosmological constant problem. Bonus points if your solution includes a dark matter candidate and/or explains the baryon asymmetry of the universe.

At some level, every talk is a job talk, since you never know whether your future employer might be in the audience. But a “real” job talk requires a lot of preparation, so start early and make sure to give a practice talk in front of a live audience to get feedback. When I applied to MIT, my job talk was scheduled right after a winter conference at the Aspen Center for Physics, so I thought I was going to enjoy some skiing and relaxation in the mountains before my MIT interview. Instead, after a decidedly mediocre practice talk, I realized that I had to rework my talk from scratch! So no skiing for me, but the extra effort was really worth it in the long run.

In terms of specific advice, here are three typical suggestions I make at practice job talks:

• Make sure your job talk is about you. This might seem obvious, but sometimes applicants focus on the field as a whole and minimize their own contributions. If ever there was a time to crow about your achievements, it is your job talk! So while it is important to provide the overall context for your work, focus on what you’ve done and provide some indication about what you plan to do in the future. And make sure your name is prominent in the citations throughout your talk.
• Imagine that someone only watches the first five minutes of your talk. These days, most job talks are recorded, so it may be the case that some dean will literally only watch the first five minutes to get a sense of who you are. In those first five minutes, is it clear what you work on and broadly what you’ve achieved? Even if someone watches your full hour talk, the first five minutes are important to set the stage and introduce the key themes, so give a clear picture of who you are and a clear outline (and even the punchline) right at the beginning.
• Don’t bury the lede. Academic talks shouldn’t be whodunnit mysteries. If you’ve accomplished something, say so, say it loudly, and say it often. You might even show your most important plot right at the beginning of the talk as a preview. But, you say, isn’t it more exciting to have a “reveal” at the end? It might be, if your audience is still engaged, but based on the five-minute advice above, they might not stick around for the punchline. Plus, there is still a way to pull off magic even if your audience knows exactly what is going on. If you really want a surprise ending, you can slip in a Jobsian “one more thing”, but make sure your main result is front and center.

If you have worked with me closely in a research and/or mentoring context, then there is a 99% chance that I’d be delighted to write you a letter of recommendation! If you only know me from coursework, then I might also be willing to write on your behalf, but you should first think about whether someone else might be better positioned to advocate for you.

I only write strong letters of recommendation. If I cannot write you a strong letter, I will let you know. The main question is how strong my letter can be, so please fill out this form so I have all the information I need to write persuasively on your behalf: Letter of Recommendation Request

I typically need at least 2 weeks but ideally 4 weeks to prepare a new letter. (The actual writing does not take that long, of course, but I receive many letter requests and I need to get sleep at some point.) If you are asking for a letter on a shorter time frame than that, then still fill out this form, but contact me ASAP to explain your situation.

Most likely, yes, but I loathe paper/scanned forms. Please use MIT’s DocuSign system if at all possible.

During the covid pandemic in Spring 2020, we faced difficult decisions about how to assess student understanding of the material in 8.044 (Statistical Mechanics). One student asked whether the final assignment grade could be dropped if their problem set grades were higher. In response, I posted the following message to Piazza:

We have developed the following official policy about whether it might be possible to give up the final assignment grade.

At the end of the semester, some students got together to make their opinions known:

W​e have collaborated on the following official evaluation ​of 8.044 this semester.

I appreciated their candor in telling us just how they’re feeling and making us understand. Certainly, a learning experience for everyone. Thank goodness we were on emergency pass/no record grading.

He/him/his.

I have debated many times with myself about whether I should put this information in my email signature, and I finally decided to add this information in October 2021, for reasons I explain below.

First, let me explain my long hesitation. “Jesse” is a somewhat gender ambiguous name, and I don’t mind (too much) when people add an extra “i” by mistake. It felt a bit uncomfortable to assert my gender at this point in my career when the gender ambiguity in my name (and in my past hairstyle) was part of my experience growing up. Also, physics is a rather male-dominated field, and I worried that providing my pronouns would somehow reinforce male-ness as the default for a physics professor, though I also appreciated that my reticence was probably doing so implicitly. I do like the way that providing pronouns signals an aspiration towards a more diverse and inclusive physics environment. As I often tell my students: there are as many ways to be a successful physicist as there are successful physicists. So while I didn’t give my preferred pronouns, my email signature did (and still does) have a link to the MIT Physics Community Values.

What made me change my mind to include my pronouns? I received an email from a student who put not only their pronouns but also the pronunciation of their name in their email signature. In the same way that misgendering a person is disrespectful, mispronouncing their name is as well. Providing this information seemed like a positive (albeit small) step towards making the physics community more welcoming. So while I didn’t go so far as to create an audio version of my name, I now state both my pronouns (he/him/his) and my pronunciation (JEH-see THAY-lr) in my signature.

Here is a link to press information of various kinds.

Though I loved my old custom html black and white webpage, I never got around to editting it much. In 2007, I decided to move to DokuWiki. In the wiki format, editing and viewing pages take the same amount of work, so I was hoping that my innate narcissism would drive me to actually create updated content.

What actually happened, though, is that I just kept adding items to my CV. A bloated cv helped me get tenure at MIT, but as one person I trust once told me: “your website looks like you are ready for retirement.”

So I decided that I really needed to update my website, still with a bloated cv, but at least there are some pictures! For aficionados, I started from the Jeykll Text Theme on GitHub Pages.

Until recently, I haven’t used social media personally or professionally. But at least now I have a LinkedIn profile!

Today is and is not opposite day. [h/t Adrian]